The invention relates to an engine having positive displacement chambers and an external combustion chamber, which utilizes the compression energy stored in a compressed natural gas main and compressed air in combination with the energy released during combustion of the fuel, to drive an electrical generator. Energy expended compressing the natural gas and air to high-pressures at an external source is recovered and utilized in combination with combustion of the fuel in an external combustion chamber to selectively power the engine on demand.
Internal combustion engines provide both portable and stationary power sources that have materially enhanced the development of industry throughout the world. It is well known that internal combustion engines are relatively inefficient and make use of only a portion of the available energy that may be derived from fossil fuels and other fuels available. In recent years, especially in view of the increasing costs of fuels, government regulation, as well as environmentalism, most engine manufacturers have undertaken the development of more efficient and environmentally friendly engine systems. Such developments have been in the nature of improving specific characteristics of internal combustion engines such as fuel metering, carburetor, fuel injection, valve control, fuel ignition, and the like. Although many positive results have been achieved toward fuel economy the cost of fuel to the consumer, as well as emissions to the environment, represent a disadvantage to the practical utilization of internal combustion engines. It is desirable to design and provide an engine energy producing system that minimizes utilization of various types of fuels, along with emissions, and yet provides an engine system having an energy and power output that may be utilized at or above the current efficiency of the energy and power output of conventional internal combustion engines.
Air pollution (emissions) is an ordinary byproduct of conventional internal combustion engines, which are used in most motor vehicles today. Various devices, including items mandated by legislation, have been proposed in an attempt to limit the emissions, which a conventional internal combustion engine exhausts to the atmosphere. Most of these devices have met with limited success and are often prohibitively expensive as well as complex. A cleaner more efficient alternative to the conventional internal combustion engine is needed to power vehicles and other machinery.
A compressed gas could provide a motive energy source for an engine since it could eliminate most of the usual pollutants exhausted from an internal combustion engine burning gasoline. An apparatus for converting an internal combustion engine for operation on compressed air is disclosed in U.S. Pat. No. 3,885,387 issued May 27, 1975 to Simington. The Simington patent discloses an apparatus including a source of compressed air and a rotating valve actuator, which opens and closes numerous mechanical poppet valves. The valves deliver compressed air in a timed sequence to the cylinders of an engine through adapters located in the spark plug holes. The output speed of an engine of this type is limited by the speed of the mechanical valves and in fact the length of time over which each of the valves remains open cannot be varied as the speed of the engine varies.
Another apparatus for converting an internal combustion engine for operation on steam or compressed air is disclosed in U.S. Pat. No. 4,102,130 issued Jul. 25, 1978 to Stricklin. The Stricklin patent discloses a device, which changes the valve timing of a conventional four (4)-stroke engine so that the intake and exhaust valves open once for every revolution of the engine instead of once every other revolution of the camshaft in a four (4) stroke engine. A reversing valve is provided which delivers live steam or compressed air to the intake valves and is subsequently placed in the reversed position in order to allow the exhaust valves to deliver the expanded steam or air to the atmosphere. A reversing valve of this type does not provide a reliable apparatus for varying the amount of motive fluid (gas) to be injected into the cylinders when it is desired to increase the speed of the engine. A device of the type disclosed in the Stricklin patent also requires the use of multiple reversing valves if the cylinders in a multi-cylinder engine are to be fired in a sequential fashion.
Engines having an adiabatic structure have recently come into productive use. These engines employ an adiabatic material such as a ceramic for constructing engine components including the combustion chambers and exhaust pipe. Engines of this type do not require the cooling of the engine by dissipating the internally generated heat. The heat energy possessed by the high-temperature exhaust gas, produced by the conventional combustion engine, is recovered and fed back to the engine output shaft, axles and the like to enhance engine output.
One known method of recovering exhaust gas energy is to reduce the rotational force of a turbine. This turbine is rotated by the exhaust gas using a multi-stage gear mechanism to drive the engine crankshaft. Another method of energy recovery is to effect a series connection between an exhaust turbine having a compressor for intake, and supply the output of the attached generator to a motor provided on the engine output shaft, thereby enabling the exhaust energy to be recovered for rotational energy use. Still another idea is to provide the engine with an exhaust bypass circuit; effect the series connection between the exhaust turbine having the generator and the exhaust turbine having the compressor to intake; supply the output of the generator to a motor provided on the engine output shaft; drive the compressor; and control the amount of exhaust that passes through the exhaust bypass circuit, thus running the engine in a nearly ideal state. These proposals have been disclosed in the specification of Japanese Patent Application Laid-Open (Kokai) No. 59-141712, which describes an engine equipped with an exhaust energy recovery apparatus. This is also elaborate and impracticable. However, the gear mechanisms required for these methods introduces design-specific problems. The transfer efficiency of one stage of a gear mechanism ordinarily is 90-95% and there is a decline in efficiency to about 80% with a three-stage gear mechanism. Furthermore, the nominal rotational speed of an exhaust gas turbine can be as high as 10,000 rpm. Reducing the turbine speed requires a gear mechanism having a greater number of stages, thus resulting in much lower transfer efficiency and a greater amount of frictional loss usually with accompanying increase in assembly weight. Since the rotational speed of the exhaust gas turbine is manufactured to accommodate the rotational speed of the engine, optimum engine turbine performance cannot be achieved.
With proposals described in Japanese Patent Application Laid-Open (Kokai) No. 59-141712, the engine is run in an almost ideal state by controlling the amount of exhaust gas flowing through the exhaust bypass circuit on the basis of data received from an engine velocity sensor and an engine load sensor. No control is performed to optimize the rotational speed of the exhaust turbine or the efficiency of the turbine.
An exhaust brake control system installed in an automotive vehicle equipped with an automatic or possible manual transmission is not new to the industry. The specification of Japanese patent Kokoki Publication No. 58-28414 describes an exhaust brake control system in which an exhaust brake is controlled by signals from an exhaust brake switch usually placed on the vehicle instrument panel, a throttle switch actuated based upon the amount the vehicle accelerator pedal is depressed, and a shift switch actuated by manual control of the automatic transmission. Compressed air generated during brake actuation may be stored in an accumulator for subsequent use during periods of peak power demand or even when the engine is cold.
U.S. Pat. No. 4,369,623 describes a positive displacement engine having an external combustion chamber. Solid, liquid and gaseous fuels can be burned in the external combustion chamber. This type of engine requires a fuel pump 36 which pumps the liquid or gaseous fuel to the combustion chamber (column 2, lines 49-51). This patent does not teach the use of a high-pressure fuel vessel nor the use of a high-pressure air vessel, which are capable of containing at least about 1,000 pounds per square inch (psi). Positive displacement cylinders of automobiles, such as those described in the ""623 patent are only capable of pumping air up to a maximum of about 140 psi (based on atmospheric pressure of 14 psi and a 10:1 compression ratio). This patent also does not teach or suggest utilizing the significant energy stored in compressed fuel and compressed air from an source external to the engine in combination with the energy released during combustion of the fuel in order to further reduce the amount of fuel combusted and reduce the emission produced.
There is a need for an improved combustion engine that utilizes the energy expended compressing the fuel and air to high-pressures at an external source, such as a gas station or residence, in combination with combustion of the fuel in an external combustion chamber to selectively power the engine on demand to avoid producing emissions and wasting fuel during idle at stops.
An objective of the present invention is to provide an improved combustion engine that utilizes the energy stored in compressed natural gas of a high pressure main and compressed air in combination with the energy released during combustion of the fuel to power an engine.
Another objective of the present invention is to provide an improved combustion engine having reduced emissions.
A further objective of the present invention is to provide an engine having instant-on power such that the an electrical generator powered by the engine can easily be shut down or operated at reduced power levels when electrical demand is low or non-existent.
The above objectives and other objectives are obtained by a combustion engine comprising:
at least one positive displacement chamber;
a reciprocating piston disposed in said at least one positive displacement chamber;
an external combustion chamber in communication with the positive displacement chamber for containing a mixture of compressed gas;
an ignitor in the combustion chamber constructed and arranged to ignite a fuel in the combustion chamber;
at least one valve constructed and arranged to control the flow of the compressed gas from the combustion chamber into the positive displacement chamber;
at least one exhaust valve constructed and arranged to control the flow of expanded gas from the positive displacement chamber;
a high pressure main connector for connecting a high pressure natural gas main line to the combustion chamber constructed;
a high pressure main valve in communication with the high pressure main connector and combustion chamber for controlling the flow of natural gas from the high pressure natural gas main line to the combustion chamber;
a high-pressure air vessel in communication with the combustion chamber;
at least one valve for controlling the flow of pressurized air from the high-pressure air vessel to the combustion chamber; and
at least one external valve constructed and arranged to fill the high-pressure air vessel with compressed air from an external pressurized air source.
Also provided is a fast response time electrical generator that utilizes the compression energy in compressed natural gas from a high pressure main line comprising:
a generator having an electric output connector; and
an engine connected to the generator, wherein the engine comprises;
at least one positive displacement chamber;
a reciprocating piston disposed in said at least one positive displacement chamber;
an external combustion chamber in communication with the positive displacement chamber for containing a mixture of compressed gas;
an ignitor in the combustion chamber constructed and arranged to ignite a fuel in the combustion chamber;
at least one valve constructed and arranged to control the flow of the compressed gas from the combustion chamber into the positive displacement chamber;
at least one exhaust valve constructed and arranged to control the flow of expanded gas from the positive displacement chamber;
a high pressure main connector for connecting a high pressure natural gas main line to the combustion chamber constructed;
a high pressure main valve in communication with the high pressure main connector and combustion chamber for controlling the flow of natural gas from the high pressure natural gas main line to the combustion chamber;
a high-pressure air vessel in communication with the combustion chamber;
at least one valve for controlling the flow of pressurized air from the high-pressure air vessel to the combustion chamber; and
at least one external valve constructed and arranged to fill the high-pressure air vessel with compressed air from an external pressurized air source.
The invention further provides a method of making electricity and recovering the compression energy in an engine comprising:
supplying compressed natural gas from a high pressure main line to a combustion chamber;
supplying compressed air from a high pressure air vessel to the combustion chamber from the high-pressure air vessel;
burning said fuel and air in said combustion chamber to form a compressed combustion gas;
opening an intake valve and supplying said compressed combustion gas to a positive displacement chamber containing a reciprocating piston such that said compressed combustion gas expands forcing said piston in a direction that increases the volume of the positive displacement cylinder to form an expanded gas;
closing said intake valve and opening an exhaust valve and allowing the expanded gas to exit said displacement chamber while said piston is moving in a direction which decreases the volume of the positive displacement chamber to provide a exhaust gas and thereby produce rotational energy; and driving an electrical generator with said rotational energy to produce electricity.
The present invention has an advantage over prior art engines in that the significant compression energy of compressed natural gas in a high pressure main and compressed air is utilized in combination with the energy released during combustion of the natural gas to power an engine. The significant energy expended during compression of the natural gas and air can be recovered during use of the engine, such as the production of electricity.
Another advantage of the present invention is that it provides instant-on power, such that combustion can be shut down during non-use, as well as operation at reduced power levels.